These devices have ARMv6 processors and are not compatible with Firefox for Android. We are working on ARMv6 support: 

The HTC Dream or T-Mobile G1 I have been finding in searches has a 528 MHz Qualcomm MSM7201A and only 192 MB RAM. This cpu is a '''ARMv6''' when a ARMv7 is required to run mobile Firefox for Android 2.2+. Edit as it is in this list: https://wiki.mozilla.org/Mobile/Platforms/Android These devices have ARMv6 processors and are not compatible with Firefox for Android. We are working on ARMv6 support: HTC Dream (T-Mobile G1, Android Dev Phone 1) The good news is that Mozilla is looking to try and get ARMv6 mobile Firefox releases in future. However if the above is your phone, it may not work well when the minimum recommended for ARMv7 is 800MHz+ and 512+MB Ram. There are third-party ARMv6 builds of mobile Firefox that you can try at your own risk at http://forum.xda-developers.com/showthread.php?p=25855563 Or if you do not mind being a Tester, then there are these unstable Nightly builds (of 17.0a1 currently) which gets checkins each day so updates happens pretty much each day. http://nightly.mozilla.org (select the ARMv6 download option)